Volcanic Activity Summary: AVO is lowering the Aviation Color Code and Alert Level at Cleveland volcano to UNASSIGNED. No volcanic activity of significance has been detected at Cleveland since late January 2009. Satellite images have shown no evidence of ash emission or thermal anomalies in the summit area. Because Cleveland is not monitored in real-time with a seismic network, we cannot confidently state that the volcano has returned completely to a background level of quiescence. Therefore, we use the term UNASSIGNED to characterize the state of the volcano and hazards.

Cleveland volcano has been intermittently active for a number of years with pauses of months between minor ash explosions. Additional ash events can occur without warning and, since the volcano is unmonitored in real-time, ash clouds can go undetected for several hours. AVO uses satellite imagery to evaluate the state of activity at Cleveland. Frequent periods of poor weather can prevent clear views of the volcano for weeks at a time.

Remarks: Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about about 75 km (45 mi.) west of the community of Nikolski, and 1500 km (940 mi.) southwest of Anchorage. The volcano's most recent significant eruption began in February, 2001 consisting of 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. This eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The most recent minor ash emissions were observed in January 2009.

Next Notice: A new VAN will be issued if conditions change significantly or alert levels are modified. While a VAN is in effect, regularly scheduled updates are posted athttp://www.avo.alaska.edu

The Alaska Volcano Observatory is a cooperative program of the U.S. Geological Survey, the University of Alaska Fairbanks Geophysical Institute, and the Alaska Division of Geological and Geophysical Surveys.

(1) VOLCANO OBSERVATORY NOTICE FOR AVIATION (VONA)

(2) Issued:

(20090501/1631Z)

(3) Volcano:

Cleveland (CAVW# 1101-24-)

(4) Current Color Code:

UNASSIGNED

(5) Previous Color Code:

yellow

(6) Source:

Alaska Volcano Observatory

(7) Notice Number:

2009/A35

(8) Volcano Location:

N 52 deg 49 min W 169 deg 56 min

(9) Area:

Aleutians Alaska

(10) Summit Elevation:

5676 ft (1730 m)

(11) Volcanic Activity Summary:

AVO is lowering the Aviation Color Code and Alert Level at Cleveland volcano to UNASSIGNED. No volcanic activity of significance has been detected at Cleveland since late January 2009. Satellite images have shown no evidence of ash emission or thermal anomalies in the summit area. Because Cleveland is not monitored in real-time with a seismic network, we cannot confidently state that the volcano has returned completely to a background level of quiescence. Therefore, we use the term UNASSIGNED to characterize the state of the volcano and hazards.

Cleveland volcano has been intermittently active for a number of years with pauses of months between minor ash explosions. Additional ash events can occur without warning and, since the volcano is unmonitored in real-time, ash clouds can go undetected for several hours. AVO uses satellite imagery to evaluate the state of activity at Cleveland. Frequent periods of poor weather can prevent clear views of the volcano for weeks at a time.

(12) Volcanic cloud height:

Nil

(13) Other volcanic cloud information:

Nil

(14) Remarks:

Cleveland volcano forms the western half of Chuginadak Island, a remote and uninhabited island in the east central Aleutians. It is located about about 75 km (45 mi.) west of the community of Nikolski, and 1500 km (940 mi.) southwest of Anchorage. The volcano's most recent significant eruption began in February, 2001 consisting of 3 explosive events that produced ash clouds as high as 12 km (39,000 ft) above sea level. This eruption also produced a rubbly lava flow and hot avalanche that reached the sea. The most recent minor ash emissions were observed in January 2009.

A new VONA will be issued if conditions change significantly or alert levels are modified. While a VONA is in effect, regularly scheduled updates are posted athttp://www.avo.alaska.edu

VOLCANO ALERT LEVELS

NORMALVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

ADVISORYVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

WATCHVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.

WARNINGHazardous eruption is imminent, underway, or suspected.

AVIATION COLOR CODES

GREENVolcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.

YELLOWVolcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.

ORANGEVolcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway with no or minor volcanic-ash emissions [ash-plume height specified, if possible].

REDEruption is imminent with significant emission of volcanic ash into the atmosphere likely OR eruption is underway or suspected with significant emission of volcanic ash into the atmosphere [ash-plume height specified, if possible].